Hey amp experts - did I kill my amp?

smurfco

smurfco

Meatus McPrepuce
Well, kill is a strong word because it still works, but it doesn't sound as good. Here's what I did.

UK-made Vox AC15. I put it in standby mode as I put my guitars and pedals away.... and then forgot to turn it off.

For two days.

On two separate occasions :facepalm:

It was in standby the whole time. I assume I need to replace the power tubes at the very least. What are the odds I damaged other components? Do I need to replace the preamp tubes too?

Yes, I'm a moron. The light is on the top of the Vox and it isn't as obvious as my Fenders when it's been left on.
 
Anecdotally, I have a friend that left his amp on stand-by at a rehearsal space for several days & it didn't seem to degrade the tubes to the point of needing to be replaced but I'm sure it's got a lot to do with the amp & state of your tubes and all that before hand...you're not pushing high voltages, just running the heater filaments and charging caps but you can get what's known as cathode poisoning over long periods of time.

If you think your tubes are shot, it's probably not a bad idea to just grab a re-tube kit from Eurotubes or similar and just swap em.
 
Wyatt said:
Cathode poisoning is a theoritical problem but not one anyone has proven anything definitive of in guitar amps.
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curious your thoughts on the topic when there are amp builders/designers like Peavy, Hamstead & Merlin Blencowe who specifically mention the possibility...are they just needlessly recycling an old wives tale?

Edit: I don't have any reason to believe its a common occurrence (especially considering some anecdotal experience to suggest it's over blown) but I do know people who think "sleepy amp sickness" is a risk of prolonged standby state
 
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I was going to say what Wyatt did. I accidentally left my amp on standby from Tuesday night practice to Thursday night practice once and it was fine, tubes and all.
 
It's not that I don't think cathode poisoning can happen. But discussions have been mostly theorical, there don't seem to be any first-hand accounts.

Maybe cathode poisoning happens, but how much over how long? Is it a percentage of lost tube life? How large of a percent is significant? There are plenty of stories of people leaving on standby for several weeks with no noticable ill effects. Others may have a single tube die. But did it die from cathode poisoning or old age? There is no consistancy.

Tubes are consumables...they all wear out eventually. So...ultimately...who cares? People worry about all these potential issues and debates that never seem to have any real impact on the day to day use of a consumer product.
 
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I don't think much has happened at all. Yes some tube life is loss but that is negligible. I look at it in reference with similarity to X-Ray Tubes. These tubes are always on and are on Standby until the next patient is X-Ray'd. In regards to smufco's amp, as long as adequate ventilation was there to properly cool during idle, no issues should be present.
 
It certainly won't hurt to swap out power tubes and bias. Then fire up the amp and see how it sounds.
I'm thinking preamp tubes are probably ok but if you still feel the tone is suffering, they are inexpensive enough to replace too.
I'd be surprised if anything was damaged besides tubes...
 
Good responses here, I'm thinking your power tubes may have been on their way out. You've basically had 96 hours of extra very light use on them, standby just keeps them heated up but you aren't driving them at all really. Preamp tubes are probably fine, I'd just start with replacing the power tubes. As gtrjunior said preamp tubes are easy and cheap to swap out.
 
gtrjunior said:
It certainly won't hurt to swap out power tubes and bias. Then fire up the amp and see how it sounds.
I'm thinking preamp tubes are probably ok but if you still feel the tone is suffering, they are inexpensive enough to replace too.
I'd be surprised if anything was damaged besides tubes...
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Ac15 is Cathode Biased. No need to bias after a tube swap :embarrassed:

:grin:
 
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